System and method for monitoring water contamination when performing subterranean operations

ABSTRACT

A method and system for monitoring groundwater quality at or near a wellbore are disclosed. A monitoring sensor is coupled to the groundwater and detects at least one characteristic of the groundwater. The monitoring sensor is a Multivariate Optical Computer (“MOC”) and is optically coupled to the groundwater

BACKGROUND

To produce hydrocarbons (e.g., oil, gas, etc.) from a subterranean formation, wellbores may be drilled that penetrate hydrocarbon-containing portions of the subterranean formation. The portion of the subterranean formation from which hydrocarbons may be produced is commonly referred to as a “production zone.” In some instances, a subterranean formation penetrated by the wellbore may have multiple production zones at various locations along the wellbore.

Hydrocarbons such as oil and gas are commonly used in a number of applications and industries. Subterranean operations are performed throughout the world to meet the increasing demand for hydrocarbons. However, subterranean operations may have an adverse impact on the environment, necessitating a balanced approach that minimizes the impact on the environment while maintaining operational efficiency.

One of the steps in performing subterranean operations involves drilling a wellbore in a desired hydrocarbon bearing formation. During drilling operations, a drill string including a drill bit may be directed downhole. The drill bit may be rotated and penetrates the formation forming a wellbore therein. In some applications, as the wellbore extends through the formation, a casing may be disposed therein. The drilling operations continue until the wellbore reaches a desired depth.

However, hydrocarbon bearing formations are often located adjacent to or otherwise near sources of groundwater. Accordingly, there is a risk that when drilling a wellbore or during subsequent subterranean operations, materials such as, for example, hydrocarbon gasses, benzene, or other injected fluids used in performance of subterranean operations may leak from the wellbore and contaminate the sources of groundwater nearby. As a result, those residing proximate to an area where subterranean operations are being performed need to periodically take water samples to ensure that the groundwater is not contaminated with hydrocarbons and/or injections fluids. Moreover, in instances where multiple operators are performing subterranean operation proximate to an area, once a contamination is detected, it is often not clear which of the operators caused the contamination.

It is therefore desirable to develop methods and systems to monitor a wellbore and detect wellbore leaks in real-time.

BRIEF DESCRIPTION OF THE DRAWING(S)

The present disclosure will be more fully understood by reference to the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings, in which like reference numbers refer to like parts throughout the views, wherein:

FIG. 1 is a system for performing subterranean operations in accordance with an illustrative embodiment of the present disclosure.

FIG. 2 is a system for performing subterranean operations in accordance with another illustrative embodiment of the present disclosure.

FIG. 3 is a Multivariate Optical Computer (“MOC”) in accordance with an illustrative embodiment of the present disclosure.

FIG. 4 depicts an MOC applied to a transparent or partially transparent fluid in accordance with an embodiment of the present disclosure.

FIG. 5 depicts an implementation of a system in accordance with an illustrative embodiment of the present disclosure in the reflectance mode.

FIG. 6 depicts a multi-analyte configuration in time domain to simultaneously identify a plurality of selected materials.

FIG. 7 depicts a multi-analyte configuration in parallel processing domain to simultaneously identify a plurality of selected materials.

The disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the disclosure being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

DETAILED DESCRIPTION OF THE DISCLOSURE

For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communication with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.

For the purposes of this disclosure, computer-readable media may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Computer-readable media may include, for example, without limitation, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk drive), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), and/or flash memory; and/or any combination of the foregoing.

The term “uphole” as used herein means along the drillstring or the wellbore hole from the distal end towards the surface, and “downhole” as used herein means along the drillstring or the wellbore hole from the surface towards the distal end. The terms “couple” or “couples” as used herein are intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect mechanical or electrical connection via other devices and connections. Similarly, the term “communicatively coupled” as used herein is intended to mean either a direct or an indirect communication connection. Such connection may be a wired or wireless connection such as, for example, Ethernet or LAN. Such wired and wireless connections are well known to those of ordinary skill in the art and will therefore not be discussed in detail herein. Thus, if a first device communicatively couples to a second device, that connection may be through a direct connection, or through an indirect communication connection via other devices and connections. The term “fluidically coupled” as used herein is intended to mean that there is either a direct or an indirect fluid flow path between two components. Finally, the term “optically coupled” as used herein is intended to mean that light transmitted and/or reflected by one component may be received by another component.

Illustrative embodiments of the present invention are described in detail herein. In the interest of clarity, not all features of an actual implementation may be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the specific implementation goals, which may vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure.

To facilitate a better understanding of the present invention, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the invention. Embodiments of the present disclosure may be applicable to horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean formation. Embodiments may be applicable to injection wells as well as production wells, including hydrocarbon wells.

The present invention is directed to improving performance of subterranean operations and more specifically, to a method and system for monitoring groundwater quality at or near a wellbore.

Turning now to FIG. 1, a system in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference numeral 100. As shown in FIG. 1, a hydrocarbon containing formation 102 may include a number of layers or strata 104, 106, 108, 110. Although four layers are shown in the illustrative embodiment of FIG. 1, as would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, any number of different layers may be present in the formation 100. Moreover, the different layers may or may not be horizontally arranged as shown in the illustrative embodiment of FIG. 1.

A wellbore 112 is drilled into the formation 102. The wellbore 112 may be a vertical, horizontal or deviated wellbore, or a combination thereof. In the illustrative embodiment of FIG. 1, the wellbore 112 extends vertically through the layers 106, 104, 108 and horizontally through a hydrocarbon bearing layer 110. Typically, as the wellbore 112 is drilled in the formation 102, one or more casing strings may be used to case the wellbore 112. For instance, a first casing string 114 may be cemented in place at a first portion of the wellbore 112 with a second casing string 116 and a third casing string 118 positioned at a second and a third portion of the wellbore 112. With the casing strings 114, 116, 118 in place and the wellbore 112 drilled as desired into the formation 102, an operator may perform a number of desired subterranean operations. For instance, in the illustrative embodiment of FIG. 1, perforating operations are performed to create perforations 120 in the formation to enhance production of hydrocarbons from the formation 102.

Typically, one or more layers of the formation 102 traversed by the wellbore 112 may include a groundwater interval 106. Many subterranean operations, such as, for example, drilling operations and perforating operations, entail pumping one or more injection fluids into the wellbore 112. Additionally, as hydrocarbons are retrieved from the formation, they are directed to the surface through the wellbore 112. In order to preserve the quality of groundwater in the groundwater interval 106, it is desirable to ensure that hydrocarbons or injections fluids utilized in performance of subterranean operations do not leak into the groundwater interval 106.

In accordance with an embodiment of the present disclosure, one or more pressure sensors may be placed in an annular space in the casing string. In the illustrative embodiment of FIG. 1, a pressure sensor 122 is placed in an annulus between the first casing string 114 and the second casing string 116. The pressure sensor 122 may monitor the pressure in the annulus in order to determine if the cement job of the second string 116 has failed. In the illustrative embodiment of FIG. 1, this would be one of the primary areas of failure that can result in the contamination of groundwater in the groundwater interval 106, specially when stimulating the wellbore 112 under high pressures. In certain embodiments, the pressure sensor 122 may be a surface pressure monitor positioned at the wellhead.

A monitoring sensor 124 may be positioned in an annulus between the outermost casing (in this case, the first casing 114) and the wellbore 112 wall in the wellbore region corresponding to the groundwater interval 106. In certain embodiments, the monitoring sensor 124 may be run in a conduit or side string that is run and cemented with surface casing and then directionally perforated (perforation 126) into the water zone in the groundwater interval 106. Accordingly, the monitoring sensor 124 may be devised to interface with the water in the groundwater interval 106 by being fluidically coupled thereto. The monitoring sensor 124 may then detect the presence and/or concentration of selected characteristics in the groundwater interval. The term “selected characteristic” as used herein refers to any characteristic whose presence in the groundwater may be indicative of an undesirable leak into the groundwater interval. As used herein, the term “characteristic” refers to a chemical, mechanical, or physical property of a substance. The characteristic may further refer to a chemical, mechanical, or physical property of a product resulting from a chemical reaction transpiring within the groundwater fluid. A characteristic of a substance may include a quantitative value of one or more chemical components therein. Illustrative characteristics of a substance that can be monitored with the optical computing devices disclosed herein can include, for example, chemical composition (e.g., identity and concentration in total or of individual components), impurity content, pH, temperature, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, combinations thereof, temperature, and the like. Other example characteristics may include, but are not limited to, the presence or concentration of hydrocarbons, various injection fluids, salts (e.g., NaCl, KCl,), polymers, fracking fluids and materials, sand, ions (e.g. Ba, Ca, F, I, K, Mg, Mn, Na, Sr, etc.), cementing compounds, and tracer or nano-tracer elements.

Creation of such directional perforations is know to those of ordinary skill in the art and will therefore, not be discussed in detail herein. In certain implementations, the monitoring sensor 124 may be retrievable. In certain embodiments, the monitoring sensor 124 may be hung off of a wire in the annulus. The monitoring sensor 124 may be designed to be communicatively coupled to an information handling system (not shown). The information handling system may be integrated with the monitoring sensor 124 or it may be placed at or near the surface or may be remotely located from the wellbore 112. The monitoring sensor 124 may be wired, wireless, electromagnetic, or acoustic.

FIG. 2 depicts a system in accordance with another illustrative embodiment of the present disclosure denoted generally with reference numeral 200. As shown in FIG. 2, a hydrocarbon containing formation 202 may include a number of layers or strata 204, 206, 208, 210. Although four layers are shown in the illustrative embodiment of FIG. 2, as would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, any number of different layers may be present in the formation 200. Moreover, the different layers may or may not be horizontally arranged as shown in the illustrative embodiment of FIG. 2.

A wellbore 212 is drilled into the formation 202. The wellbore 212 may be a vertical, horizontal or deviated wellbore, or a combination thereof. In the illustrative embodiment of FIG. 2, the wellbore 212 extends vertically through the layers 206, 204, 208 and horizontally through a hydrocarbon bearing layer 210. Typically, as the wellbore is drilled in the formation 202, one or more casing strings may be used to case the wellbore. For instance, a first casing string 214 may be cemented in place at a first portion of the wellbore 212 with a second casing string 216 and a third casing string 218 positioned at a second and a third portion of the wellbore 212. With the casing strings 214, 216, 218 in place and the wellbore 212 drilled as desired into the formation 202, an operator may perform a number of desired subterranean operations. For instance, in the illustrative embodiment of FIG. 2, perforating operations are performed to create perforations 220 in the formation 202 to enhance production of hydrocarbons from the formation 202.

Typically, one or more layers of the formation 202 traversed by the wellbore 212 may include a groundwater interval 206. Many subterranean operations, such as, for example, drilling operations and perforating operations, entail pumping one or more injection fluids into the wellbore 212. Additionally, as hydrocarbons are retrieved from the formation 202, they are directed to the surface through the wellbore 212. In order to preserve the quality of groundwater in the groundwater interval 206, it is desirable to ensure that hydrocarbons or injections fluids utilized in performance of subterranean operations do not leak into the groundwater interval 206.

In accordance with an embodiment of the present disclosure, a Data Acquisition and Processing Unit (“DAPU”) 222 may be positioned at the surface. The DAPU 222 may include a monitoring sensor 224. The DAPU 222 may be fluidically coupled to the groundwater interval 206. In one embodiment, a side string 226 may run from the surface and may be fluidically coupled to the groundwater interval 206 through a perforation 228 into the groundwater interval 206. In certain embodiments, the side string 226 may be cemented in place. A pump, such as, for example, a venturi type pump, may be coupled to the DAPU 222 and/or the side string 226 to pump water from the groundwater interval 206 to the DAPU 222 located at the surface. A sample may then be obtained at the DAPU 222 and analyzed to detect any water contamination.

As discussed in more detail below, the monitoring sensor 224 integrated with the DAPU 222 may detect the presence and/or concentration of selected materials in the groundwater interval. By continuously pumping water from the groundwater interval 206 to the DAPU 222 through the side string 226, water quality may be monitored in real time. In certain embodiments, the DAPU 222 may include an information handling system to process and/or respond to signals from the monitoring sensor 224. For instance, as discussed below, the information handling system of the DAPU 222 may notify an operator when concentration of one or more selected materials exceeds a preset threshold value.

Moreover, the DAPU 222 and the side string 226 may be designed so that the DAPU 222 can be detachably attached thereto permitting selective coupling and de-coupling form the side string 226. Specifically, the side string 226 may be cemented in place and may include a connection port at the surface that is couplable to the DAPU 222. In this implementation, the DAPU 222 may be moved from one wellbore to another to periodically check water quality at two or more wellbores. This implementation may be of particular value in instances where a plurality of wellbore are operational proximate to one another. Moreover, because the DAPU 222 is located at the surface, there is less constraint placed on the size, shape, and energy consumption of the monitoring sensor 224. Finally, failure or damage to any components of the DAPU 222 may be easily addressed at the surface without the need to remove components from the wellbore 212. Accordingly, the implementation of FIG. 2 may be used to provide a continuous or intermittent monitoring of water in the groundwater interval 206 in a manner similar to that described in conjunction with FIG. 1.

In certain embodiments, the monitoring sensor 124, 224 discussed in conjunction with FIGS. 1 and 2 may be an Opto-analytical device such as a Multivariate Optical Computer (“MOC”) including an Integrated Computational Element (“ICE”) 302 as shown in and discussed in conjunction with FIG. 3.

An MOC is a real-time optical computer that uses light instead of complex circuitry of a conventional electronic processor to perform calculations. As discussed in more detail below, in accordance with certain implementations of the present disclosure, an MOC may be optically coupled to a sample (e.g., a groundwater sample) to be analyzed. As would be appreciated by those of ordinary skill, having the benefit of this disclosure, the monitoring sensor 124, 224 may be coupled to the groundwater in any suitable manner depending on the type of the sensor used. Specifically, the while the MOC may be optically coupled to the sample, other types of sensors may be coupled to the sample in other suitable manners, known to those of ordinary skill in the art having the benefit of the present disclosure. AN MOC may be used to measure concentration of various characteristics under a wide range of conditions. Specifically, when light (and/or other electromagnetic radiations) interacts with a substance, the physical, mechanical, and chemical information of the substance may be optically encoded into the interacted light (and/or electromagnetic radiations) which may transfer through or be reflected from the material. AN MOC acts as an optical computational processor that extracts this information. Specifically, light that has interacted with a material of interest is directed to an MOC. The MOC conceptually splits this interacted light into two components. The first component may be light recognized from the compound(s) of interest and the second component may be light associated with interferents (i.e., everything else). The separation of light into separate components may be accomplished using an ICE as discussed in more detail in conjunction with FIG. 3. The ICE instantaneously processes the light and provides an optical signal that is related to the characteristic of interest. Accordingly, the light related to the characteristic of interest may be detected in real time and displayed to an output. Further, the processed signal from the ICE may be provided as a calibrated voltage signal and the chemical or physical information may be detected and utilized in real-time.

Utilizing an MOC as a monitoring sensor provides several advantages. First, the MOC provides measurements at the speed of light thereby providing almost instantaneous analysis of a desired sample in situ (e.g., on the field). Moreover, the MOC is an accurate sensor that can distinguish between similar substances thereby providing an accuracy similar to that of a laboratory grade spectrometer together with the simplicity and reliability of a rugged filter photometer. The MOC includes passive optical components that can withstand high temperatures and pressures associated with performance of subterranean operations. Additionally, the small size, long operational life, and low energy consumption of an MOC make it particularly suitable for use in conjunction with subterranean operations. Accordingly, an MOC can be used to detect any characteristics that are optically active in any region of the electromagnetic spectrum (e.g., Ultraviolet, Visible, Infrared, X-Ray, Vacuum ultraviolet, microwave, radio wave, etc.). For instance, the compounds that can be detected by the MOC may include, but are not limited to, liquids (e.g., oils, water, etc.), gases (e.g., CH4, CO2, H2S, etc.), solids (e.g., organic materials, plastics, minerals, salts, etc.), slurries, powders, and/or combinations thereof.

Additionally, an MOC provides a compact means for processing and evaluating data from a groundwater sample and facilitates performance of analysis that would otherwise require a plurality of different sensors. Due to its small size and its integrated processing capabilities, the MOC may be integrated into a well bore. For instance, the MOC may be placed in an annulus between the outermost casing and the wellbore wall in the wellbore region corresponding to the groundwater interval (as shown in FIG. 1). Accordingly, the MOC may analyze various characteristics of a groundwater interval (discussed above) while integrated within a well bore (as shown in FIG. 1) or placed at the well bore surface (as shown in FIG. 2). The MOC's compact structure facilitates efficient use of space which is a valuable commodity when performing subterranean operations.

Turning now to FIG. 3, an Opto-analytical device is denoted generally with reference numeral 300. In certain implementations, the Opto-analytical device 300 may be an MOC. The Opto-analytical device 300 may include the ICE 302 which may be operational to receive electromagnetic radiation 301 from a sample 304. The sample 304 may be obtained from the groundwater interval 106 through the perforation 126. Note that although the operation of the ICE 302 is discussed in an illustrative application to the configuration of FIG. 1, the same is applicable to the embodiment of FIG. 2.

ICE 302 may be configured to detect a characteristic of sample 304 based on the received electromagnetic radiation 301. When electromagnetic radiation interacts with sample 304, unique physical and chemical information about sample 304 may be encoded in electromagnetic radiation 301 that is reflected from, transmitted through or radiated from sample 304. Information associated with each different characteristic may be encoded in electromagnetic radiation 301.

As used herein, the term “electromagnetic radiation” refers to electromagnetic waves of any wavelength, including radio waves, microwave radiation, infrared and near-infrared radiation, visible light, ultraviolet light, X-Ray radiation and gamma ray radiation. Electromagnetic radiation 301 may come from any number of sources. For example, electromagnetic radiation 301 may originate from heat emanating from sample 304. Electromagnetic radiation 301 may be in the ultraviolet (UV) spectrum and may also be UV radiation emanating or fluorescing from sample 304. In other embodiments, electromagnetic radiation 301 may be derived from an active electromagnetic source (e.g., infrared, UV, X-Ray, visible light, etc.) that illuminates sample 304. The electromagnetic source may be located within the annulus or otherwise integrated into the monitoring sensor 124. In some embodiments, electromagnetic radiation may be derived from heat emanating from one or more portions of the sample 304.

Sample 304 may be any type of material or area that may have one or more characteristics that may be of interest. For example, in the context of groundwater monitoring, sample 304 may be the water from the groundwater interval 106 which may contain one or more selected materials. Accordingly, electromagnetic radiation 301 received from sample 304 may include information associated with any number of characteristics associated with sample 304. For example, electromagnetic radiation 301 from the sample 304 may include information indicating the temperature of the water and concentration of selected materials in the water. As another example, electromagnetic radiation 301 may include spectral signatures associated with the presence and concentration of fluids or solids in the sample 304.

ICE 302 may be configured to receive electromagnetic radiation 301 and detect a particular characteristic of sample 304 based on a correlation associated with the particular characteristic included in electromagnetic radiation 301. The underlying theory behind using ICE for conducting analyses is described in more detail in the following commonly owned United States patents and patent application Publications, each of which is incorporated herein by reference in its entirety: U.S. Pat. Nos. 6,198,531; 6,529,276; 7,123,844; 7,834,999; 7,911,605; and 7,920,258; and U.S. Patent Publication Nos. 2009/0219538; 2009/0219539; and 2009/0073433.

ICE 302 may include a plurality of alternating layers of optical elements (e.g., silicon, germanium, water, or other materials of interest) with transmissive, reflective, and/or absorptive properties suitable for detecting a characteristic of interest. For example, the alternating layers may be niobium pentoxide (Nb₂O₅), and Niobium, Silicon and quartz (SiO₂) deposited on a substrate (e.g., glass, diamond, quartz, sapphire, ZnSe, ZnS, Ge, Si, etc.). In general, the materials forming the alternate layers may consist of materials that have indices of refraction that differ from one another, e.g., one has a low index of refraction and the next has a high index of refraction. Other suitable materials for the layers may include, but are not limited to, germanium and Germania, MgF, SiO, and other thin film capable materials familiar to those skilled in the art. The number of layers and the thickness of the layers may be determined and constructed from the spectral attributes of the characteristic of interest as determined from a spectroscopic analysis of the characteristic using a conventional spectroscopic instrument. The combination of layers may correspond or be related to the spectral correlation of the characteristic of interest.

The multiple layers may have different refractive indices. By properly selecting the materials of the layers and their spacing, ICE 302 can be made to selectively transmit, absorb, and/or reflect predetermined fractions of light at different wavelengths. Each wavelength may be given a pre-determined weighting or loading factor. The thicknesses and spacing of the layers may be determined using a variety of approximation methods from the spectrograph of the characteristic of interest. These methods may include inverse Fourier transform (IFT) of the optical transmission spectrum and structuring the optical calculation device as the physical representation of the IFT. The approximations convert the IFT into a structure based on known materials with constant refractive indices. In addition to solids, ICE 302 may also contain liquids and/or gases in combination with solids to create the desired layers. ICE 302 may also include holographic optical elements, gratings, and/or acousto-optic elements, for example, that may create the transmission, reflection, and/or absorption properties of interest for the layers of ICE 302.

The weightings that ICE 302 layers apply at each wavelength are set such that they relate or correlate to the regression weightings described with respect to a known equation, or data, or spectral correlation of the characteristic of interest. The intensity of transmitted, absorbed, or reflected electromagnetic radiation 303 is related to the amount (e.g., concentration) of the characteristic of interest associated with sample 304. Accordingly, ICE 302 may be configured to detect a particular characteristic of sample 304 based on the correlation associated with the particular characteristic that is included in received electromagnetic radiation 301.

In addition, significant benefits may be realized by combining the outputs of two or more integrated computational elements with one another when analyzing a single characteristic of interest. Specifically, significantly increased detection accuracy may be realized. Analysis techniques utilizing combinations of two or more ICE are described in commonly owned U.S. patent application Ser. Nos. 13/456,255; 13/456,264; 13/456,283; 13/456,302; 13/456,327; 13/456,350; 13/456,379; 13/456,405; and 13/456,443; each filed on Apr. 26, 2012 and incorporated herein by reference in its entirety.

Opto-analytical device 300 may include a detector 306 configured to receive transmitted electromagnetic radiation 303 from ICE 302. Detector 306 may include any suitable apparatus, system, or device configured to detect the intensity of transmitted electromagnetic radiation 303 and generate a signal related to the intensity of transmitted electromagnetic radiation 303 received from ICE 302. For example, detector 306 may be configured to generate a voltage related to the intensity of transmitted electromagnetic radiation 303. Detector 306 may communicate the signal (e.g., voltage signal) related to the intensity of transmitted electromagnetic radiation 303 to a processing unit 308.

Processing unit 308 may be configured to receive the signal communicated from detector 306 and correlate the received signal with the characteristic which ICE 302 is configured to detect. For example, ICE 302 may be configured to detect the temperature of sample 304 and the intensity of transmitted electromagnetic radiation 303 transmitted from ICE 302 may accordingly be related to the temperature of sample 304. Accordingly, detector 306 may generate a voltage signal based on the intensity of electromagnetic radiation 303 and may communicate the voltage signal to processing unit 308. Processing unit 308 may then correlate the received voltage signal with a temperature such that processing unit 308 may determine a temperature of sample 304.

Processing unit 308 may be an information handling system which can interpret and/or execute program instructions and/or process data associated with opto-analytical device 300. In certain implementations, the processing unit 308 may be, without limitation, a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and/or execute program instructions and/or process data. In some embodiments, the processing unit 308 may interpret and/or execute program instructions and/or process data stored in one or more computer-readable media included in processing unit 308.

The computer-readable media may be communicatively coupled to the processing unit 308 and may include any system, device, or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). The computer-readable media may retain data after power to processing unit 308 is turned off. In accordance with some embodiments of the present disclosure, the computer-readable media may include instructions for determining one or more characteristics of sample 304 based on signals received from detector 306.

ICE 302 may also be configured to reflect portions of electromagnetic radiation 301 not related to the characteristic of interest as reflected electromagnetic radiation 305. In some embodiments, ICE 302 may reflect electromagnetic radiation 305 toward another detector (not expressly shown in FIG. 3). The detector configured to receive reflected electromagnetic radiation 305 may be configured to generate a signal associated with reflected electromagnetic radiation 305 and communicate the signal to processing unit 308. Processing unit 308 may use the signal associated with electromagnetic radiation 305 to normalize the signal associated with transmitted electromagnetic radiation 303. In alternative embodiments, ICE 302 may be configured such that reflected electromagnetic radiation 305 may be related to the characteristic of interest and transmitted electromagnetic radiation 303 may be related to other characteristics of sample 304.

Opto-analytical device 300 may be configured to detect and determine a characteristic of sample 304 based on electromagnetic radiation 301 received from sample 304. Opto-analytical device 300 may include any number of ICEs 302 and associated detectors 306 configured to detect any number of characteristics of sample 304. Processing unit 308 may accordingly be configured to determine one or more properties of sample 304 based on the different characteristics detected by different ICEs 302 and associated detectors 306. In some embodiments processing unit 308 may be configured to store collected data associated with a detected characteristic in any suitable storage medium such as a computer-readable medium. The collected data may then be retrieved at a later time and may be analyzed and processed to determine various properties of sample 304. In embodiments where opto-analytical device 300 is integrated with a drilling tool, processing unit 308 may be configured to communicate information associated with a detected characteristic to a well site using any suitable communication system.

When monitoring more than one characteristic at a time, various configurations for multiple ICEs 302 may be used, where each ICE 302 has been configured to detect a particular characteristic of interest. In some embodiments, the characteristic may be analyzed sequentially using multiple ICEs 302 that are presented to a single beam of electromagnetic radiation being reflected from or transmitted through a sample.

In some embodiments, multiple ICEs 302 can be located on a rotating disc, where the individual ICEs 302 are exposed to the beam of electromagnetic radiation for a short period of time. This implementation is discussed in further detail in conjunction with FIG. 6. Advantages of this approach may include the ability to analyze multiple characteristics using a single optical computing device and the opportunity to assay additional characteristics simply by adding additional ICEs to the rotating disc. In various embodiments, the rotating disc can be turned at a frequency of about 1 RPM to about 30,000 RPM such that each characteristic in a sample is measured rapidly. In some embodiments, these values may be averaged over an appropriate time domain (e.g., about 1 millisecond to about 1 hour) to more accurately determine the sample characteristics.

In other embodiments, multiple ICEs 302 may be placed in parallel, where each ICE 302 is configured to detect a particular characteristic of interest. This implementation is discussed in more detail in conjunction with FIG. 7. In such embodiments, a beam splitter may divert a portion of the electromagnetic radiation from the substance being analyzed to each ICE 302. Each ICE 302, in turn, may be communicatively coupled to detector 306 or array of detectors 306 configured to detect an output of electromagnetic radiation from the ICE 302. Parallel configurations of ICEs 302 may be particularly beneficial for applications that require low power inputs and/or no moving parts.

In still additional embodiments, multiple ICEs 302 may be placed in series, such that characteristics are measured sequentially at different locations and times. For example, in some embodiments, a characteristic can be measured in a first location using a first ICE 302, and the characteristic can be measured in a second location using a second ICE 302. In other embodiments, a first characteristic may be measured in a first location using a first ICE 302, and a second characteristic may be measured in a second location using a second ICE 302.

Any of the foregoing configurations for the opto-analytical device 300 may be used in combination with a series configuration in any of the present embodiments. For example, two rotating discs having a plurality of ICEs may be placed in series for performing an analysis. Likewise, multiple detection stations, each containing ICEs 302 in parallel, may be placed in series for performing an analysis.

As mentioned above, an opto-analytical device 300 may be used in accordance with embodiments of the present disclosure to detect presence and/or amount of one or more selected materials in groundwater. The detection of selected materials may also be used to determine an event associated with drilling a wellbore. In some embodiments, drilling of a wellbore may be modified based on the detection of the selected materials.

FIG. 4 depicts an MOC applied to a transparent or partially transparent fluid in accordance with an embodiment of the present disclosure. An illumination source 402 such as a lamp may be positioned so as to illuminate the sample obtained from the groundwater interval 106. A sample from the groundwater interval 106 is then directed through a cell 404 and the electromagnetic waves transmitted through the cell 404 are directed to ICE 406. In certain embodiments, the ICE 406 may direct emissions from the cell 404 to one or more detectors. In the illustrative embodiment of FIG. 4, the ICE 406 directs emissions from the cell 404 to a first detector 408 (Detector A) and a second detector 410 (Detector B). The light transmitted through the cell 404 is processed by ICE 406 and detectors 408 and 410. The output of the detectors 408, 410 may then be converted to an appropriate signal for communication purposes via standard electronics. For instance, in certain embodiments, the processed signal may be transmitted to an information handling system for further analysis or to notify an operator of existence and/or concentration of selected materials in the under groundwater interval 106. In the illustrative embodiment of FIG. 4 where two detectors 408, 410 are used, the signal received by the second detector (Detector B) 410 may be used to normalize the signal received by the first detector (Detector A) 408 for light intensity variations, scattering effects, window contamination, etc.

In certain embodiments, the methods and systems disclosed herein may be used in the reflectance mode as shown in FIG. 5, in instances where the sample to be analyzed is not optically transparent. For instance, the sample obtained may contain powder, mud, or other materials. As shown in FIG. 5, an illumination source 502 such as a lamp may be positioned so as to illuminate the sample obtained from the groundwater interval 106. The electromagnetic emissions reflected by the sample are then directed to the ICE 506. In the illustrative embodiment of FIG. 5, the ICE 506 directs emissions from the cell 504 to a first detector 508 (Detector A) and a second detector 510 (Detector B). The light transmitted through the cell 504 is processed by ICE 506 and detectors 508 and 510. The output of the detectors 508, 510 may then be converted to an appropriate signal for communication purposes via standard electronics. For instance, in certain embodiments, the processed signal may be transmitted to an information handling system for further analysis or to notify an operator of the existence and/or concentration of selected materials in the under groundwater interval 106. In the illustrative embodiment of FIG. 5 where two detectors 508, 510 are used, the signal received by the second detector (Detector B) 510 may be used to normalize the signal received by the first detector (Detector A) 508 for light intensity variations, scattering effects, window contamination, etc.

The illustrative embodiments of FIGS. 4 and 5 depict a “one analyte” system whose output is limited to detection and/or concentration of one component. In certain applications in accordance with the present disclosure, it may be desirable to monitor more than one analyte at a time. A number of different MOC implementations may be used to achieve that end.

In certain embodiments, the methods and systems disclosed herein may be used in a multi-analyte configuration in time domain to simultaneously identify a plurality of selected materials as shown in FIG. 6. An illumination source 602 such as a lamp may be positioned so as to illuminate the sample obtained from the groundwater interval 106. A sample from the groundwater interval 106 is then directed through a cell 604 and the electromagnetic waves transmitted through the cell 604 are directed to an ICE filter wheel 606 and then to detectors 608, 610. The ICE filter wheel 606 may be compact and comprise a number of slots for installation of different ICE element. A variety of ICE elements that may be exposed to the electromagnetic waves transmitted through the cell 604 as shown in more detail in FIG. 6.

As shown in FIG. 6, in the illustrative embodiment disclosed therein six ICE elements are integrated into the ICE filter wheel 606. Accordingly, each of a plurality of selected materials or analytes may be measured individually when its respective ICE element is exposed to the beam. The ICE filter wheel 606 may be rotated at any desirable rate to detect the different selected materials. In certain embodiments, the ICE filter wheel 606 may be rotated at rates ranging from 1 RPM up to 10,000 RPM yielding a concentration value for each of the selected materials of 1 times per minute or up to 10,000 times per minute. In application, the values obtained for concentration of selected materials over time may be averaged over an appropriate time interval. For instance, the concentration of the different selected materials may be stored in a computer readable medium each time a value is obtained (e.g., 1 values per minute or 10,000 values per minute in the above example). After a certain time period (e.g., 0.1-5 minutes) the stored values may be averaged and the obtained average may be used as an indication of the concentration of the selected material in the cell 606. In certain embodiments, the determined concentration of the selected materials may be visually displayed, for example, using an information handling system.

In certain embodiments, one or more slots of the ice filter wheel 606 may initially be unused and facilitate installation of additional ICE elements as needed. The ICE filter wheel 606 may include any number of slots. For instance, in certain embodiments, the ICE filter wheel 606 may include up to 40 slots that may be utilized as needed to identify up to 40 different selected materials.

In certain embodiments, the methods and systems disclosed herein may be used in a multi-analyte configuration in parallel processing domain to simultaneously identify a plurality of selected materials as shown in FIG. 7. An illumination source 702 such as a lamp may be positioned to illuminate the sample obtained from the groundwater interval 106. A sample from the groundwater interval 106 is then directed through a cell 704 and the electromagnetic waves transmitted through the cell 704 are directed to a first ICE 706A and a second ICE 706B. Accordingly, the electromagnetic waves transmitted through the cell 704 may be split into three segments. Specifically, a primary beam from the first ICE element 706A is directed to the detector 712 and a primary beam from the second ICE element 706B is directed to a second detector 710. Additionally, a secondary beam from each of the first ICE element 706A and the second ICE element 706B is directed to a second detector 708. Accordingly, each of the detectors 710, 712 may be used to detect one of the selected materials. The absence of any moving parts and the lower power consumption of the parallel processing domain implementation render it well suited for downhole applications.

Although the illustrative embodiment of FIG. 7 is shown as being operable to detect two selected materials, in practice, the optical beam from the cell 704 may be divided into many separate beams, each directed to a corresponding ICE element. For instance, in certain embodiments, up to twenty different ICE elements may be employed together with a single light source.

Finally, in other implementations, various single or multiple analyte systems may be placed in series. This implementation is particularly useful if it is desirable to measure the concentration of selected materials at different locations. For instance, it may be desirable to measure the concentration of selected materials at different depths in the groundwater interval 106. Moreover, it may be desirable to utilize ICE elements having different light sources. For instance, a first group of ICE elements may utilize an infrared light source while a second group may utilize an ultraviolet light source. This implementation permits detection of selected materials that may be more easily detected with light of one particular wave length as compared to another.

The ability of ICE to detect hydrocarbons together with its compact nature and the long expected life and lower power requirements make it particularly suitable for this application. In some embodiments, longer expected life can be achieved by turning on the MOC whenever a measurement is desired, and then turning off the lamp and MOC in between to conserve energy and extend life. For example, the MOC may be turned on for about 30 seconds and a measurement taken, then turned off for an hour until the next measurement is taken. In this example, the energy consumed is reduced by a factor of 120 over continuous operation. Such operation is particularly important for battery implementations. Finally, we note that several MOC systems may be linked and turned on in a round robin fashion to yield data from an extended geographical region while conserving energy and communications resources.

As would be appreciated by those of ordinary skill in the art, having the benefit of the present disclosure, in certain implementations a plurality of ICE may be utilized to enhance detection of the selected materials. Significant benefits may be realized by combining the outputs of two or more ICE with one another when analyzing for a single constituent or characteristic of interest. Techniques for combining the output of two or more ICE are described in commonly owned U.S. patent application Ser. Nos. 13/456,255, 13/456,264, 13/456,283, 13/456,302, 13/456,327, 13/456,350, 13/456,379, 13/456,405, and 13/456,443, each filed on Apr. 26, 2012 and incorporated herein by reference in its entirety. Any of the techniques described herein may be carried out by combining the outputs of two or more ICE with one another. The ICE whose outputs are being combined may be associated or disassociated with the constituent or characteristic, display a positive or negative response when analyzing the constituent or characteristic, or any combination thereof.

Moreover, although specific examples of implementing an ICE are disclosed herein, other methods may be utilized to identify the selected materials without departing from the scope of the present disclosure. These methods include, but are not limited to holographic optical elements (HOE's), phase gratings, optical gratings, Digital Light Pipe (DLP) devices, liquid crystal devices, photo-acoustic devices, and even naturally occurring substances such as water (e.g., in a curvette or holder) and gasses (e.g., water vapor, CO, CO2, methane, hydrocarbon gases, NO and NOx nitrogen gases, etc).

Accordingly, the monitoring sensor 124 may monitor the water in the groundwater interval 106 for traces of one or more different materials in real-time. An operator may then designate a threshold value for a characteristic of interest. For instance, in certain implementations, a threshold value may be designated for the concentration of the selected materials in the groundwater. This threshold value may be stored in a computer readable medium communicatively coupled to the information handling system. Once monitoring sensor 124 detects one of the selected materials, the detected concentration will be compared with the threshold value by the information handling system. If it is determined that the concentration of the selected materials in the water in the groundwater interval exceeds the threshold value, the information handling system may notify the operator. In certain embodiments, the notification may be a visual or audio notification such as, for example, sounding an alarm or illuminating a warning light.

In accordance with certain implementations of the present disclosure, identification of selected materials by the monitoring sensor 124 (e.g., MOC) may be used to identify the source or path of contamination of groundwater. For example, if a contamination source is known to have a high iron or salt content, then the detection of excessive concentrations of iron or salt in the groundwater would indicate and identify the source of the contamination. Hydrocarbon sources may have unique chemical fingerprints which can be used to identify whether they are the source of the contamination or not. For example, oil from an underground formation has a different composition than refined oil leaking from an automobile onto the ground and into the groundwater. Thus, identification of the appropriate fingerprinting characteristics would enable the source of the contamination to be identified. An operator may then modify ongoing operations if the identification of the contamination source necessitates modification of ongoing operations.

In certain embodiments, an operator may implement the methods and systems disclosed herein across two or more wellbores and utilize a central information handling system to monitor groundwater contamination at each wellbore. Each wellbore may be proximate or adjacent to a corresponding groundwater interval and may be equipped with a monitoring sensor as described in conjunction with FIGS. 1 and 2. Each monitoring sensor may then be communicatively coupled to the central information handling system. The central information handling system may provide a visual rendering of status at the different wellbores and/or notify the operator of potential contamination at each wellbore or group of wellbores by detecting the presence and/or concentration of one or more selected materials. This information may be used to selectively control operation of different wellbores in response.

Moreover, in instances where multiple wellbores are operated proximate to an undergroundwater interval, the methods and systems disclosed herein may be used to identify the wellbore that has caused the contamination of the undergroundwater. Specifically, a wellbore that is being monitored in real-time using the methods and systems disclosed herein may be eliminated as a potential cause for contamination of the groundwater. Thereby, an operator may utilize the methods and systems disclosed herein to shield itself from potential liability resulting from contamination of underground water reserves.

Accordingly, quality of groundwater at or near a wellbore may by monitored and used to alarm an operator as to any potential environmental risks from hydrocarbons or injected fluid entering the groundwater system from the wellbore. Moreover, the methods and systems disclosed herein eliminate the need for drilling a second wellbore to monitor the environmental impact of performance of subterranean operations in a formation.

Therefore, the present disclosure is well-adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the disclosure has been depicted and described by reference to exemplary embodiments of the disclosure, such a reference does not imply a limitation on the disclosure, and no such limitation is to be inferred. The disclosure is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the disclosure are exemplary only, and are not exhaustive of the scope of the disclosure. Consequently, the disclosure is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects. The terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. 

What is claimed is:
 1. A system for monitoring at least one characteristic of groundwater in a subterranean formation comprising: a monitoring sensor coupled to the groundwater, wherein the monitoring sensor is operable to detect at least one characteristic of the groundwater, wherein the monitoring sensor is a Multivariate Optical Computer (“MOC”) and wherein the MOC is optically coupled to the groundwater.
 2. The system of claim 1, wherein the at least one characteristic is selected from a group consisting of chemical composition, pH, temperature, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, hydrocarbon concentration, salt concentration, ion concentration, mud fluid concentration, fracking fluid concentration, tracer concentration, and a combination thereof.
 3. The system of claim 1, wherein coupling the monitoring sensor to the groundwater interval comprises at least one of placing the monitoring sensor in the wellbore proximate to the groundwater interval and coupling the monitoring sensor to a side string wherein the side string is fluidically coupled to the groundwater interval.
 4. The system of claim 3, wherein the MOC is battery operated.
 5. The system of claim 1, wherein the monitoring sensor notifies an operator if the at least one characteristic exceeds a threshold value.
 6. A method for monitoring ground fluids when performing subterranean operations comprising: drilling a wellbore in a subterranean formation, wherein the wellbore traverses one or more strata of the subterranean formation, and wherein at least one of the one or more strata of the subterranean formation comprises a groundwater interval; coupling a monitoring sensor to the groundwater interval, wherein coupling the monitoring sensor to the groundwater interval comprises at least one of placing the monitoring sensor in the wellbore proximate to the groundwater interval and coupling the monitoring sensor to a side string wherein the side string is fluidically coupled to the groundwater interval; and detecting at least one characteristic of the groundwater interval using the monitoring sensor.
 7. The method of claim 6, wherein coupling the monitoring sensor to the groundwater interval comprises providing a perforation into the groundwater interval, wherein fluid from the groundwater interval flows to the monitoring sensor through the perforation.
 8. The method of claim 7, further comprising fluidically coupling a side string to the perforation and the monitoring sensor, wherein the monitoring sensor is detachably attached to the side string.
 9. The method of claim 6, further comprising placing a casing in the wellbore, wherein the monitoring sensor is positioned in an annulus between the casing and the wellbore.
 10. The method of claim 6, further comprising selectively turning the monitoring sensor on and off to detect the at least one characteristic of the groundwater interval using the monitoring sensor.
 11. The method of claim 6, wherein the monitoring sensor is optically coupled to the groundwater interval.
 12. The method of claim 6, wherein the monitoring sensor is a Multivariate Optical Computer (“MOC”).
 13. The method of claim 6, wherein the monitoring sensor notifies an operator if the at least one characteristic exceeds a threshold value.
 14. The method of claim 6, wherein the at least one characteristic is selected from a group consisting of chemical composition, pH, temperature, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, hydrocarbon concentration, salt concentration, ion concentration, mud fluid concentration, fracking fluid concentration, tracer concentration, and a combination thereof.
 15. A method for monitoring a characteristic of groundwater intervals corresponding to a plurality of wellbores comprising: drilling a first wellbore adjacent to a first groundwater interval; optically coupling a first monitoring sensor to the first groundwater interval; drilling a second wellbore adjacent to a second groundwater interval; optically coupling a second monitoring sensor to the second groundwater interval, wherein at least one of the first monitoring sensor and the second monitoring sensor is a Multivariate Optical Computer (“MOC”); communicatively coupling the first monitoring sensor and the second monitoring sensor to a central information handling system; monitoring a characteristic in the first groundwater interval using the first monitoring sensor; and monitoring a characteristic in the second groundwater interval using the second monitoring sensor.
 16. The method of claim 15, further comprising at least one of providing a visual rendering of data received from the first monitoring sensor and the second monitoring sensor and notifying an operator of potential contamination at the central information handling system.
 17. The method of claim 15, wherein at least one of the characteristic in the first groundwater interval and the characteristic in the second groundwater interval is selected from a group consisting of chemical composition, pH, temperature, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, hydrocarbon concentration, salt concentration, ion concentration, mud fluid concentration, fracking fluid concentration, tracer concentration, and a combination thereof.
 18. The method of claim 15, further comprising selectively turning at least one of the first monitoring sensor and the second monitoring sensor on and off to monitor the characteristic in the first groundwater interval and the characteristic in the second groundwater interval.
 19. The method of claim 15, wherein at least one of the first monitoring sensor and the second monitoring sensor is battery operated.
 20. The method of claim 15, wherein the central information handling system notifies an operator if at least one of the characteristic of the first groundwater interval and the characteristic of the second groundwater interval exceeds a threshold value. 